DFS Pregel performance vs simple Java DFS implementation

DFS Pregel performance vs simple Java DFS implementation

Hi,

Considering a directed graph with 15,000 vertices and 14,000 edges, I wonder
why GraphX (Pregel) takes much more time than the java implementation of a
graph to get all the vertices from a vertex to the leaf?
By the nature of the graph, we can almost consider it as a tree.

The java implementation: A few seconds
The Graphx implementation: Several minutes